Immediate Postoperative Disappearance of Retro-Odontoid "Pseudotumor".

Objective: The authors present reports of 2 cases in which there was manifest atlantoaxial instability and presence of retro-odontoid pseudotumor. The retro-odontoid tumor disappeared in the immediate postoperative phase after surgery, which involved facetal distraction and atlantoaxial fixation. The cases are discussed. Although regression of the retro-odontoid pseudotumor has been reported after atlantoaxial fixation, its disappearance in the immediate postoperative phase has not been recorded.

Methods: Two patients (42 years and 16 years old) presented with progressive quadriparesis. Investigations revealed presence of retro-odontoid "pseudotumor" and evidence of cord compression. There was radiologic evidence of atlantoaxial instability in both cases. Both patients were treated by atlantoaxial lateral facet distraction and fixation. No attempt was made to directly manipulate or handle the retro-odontoid tissue.

Results: The patients had remarkable clinical improvement after surgery. Immediate postoperative imaging showed disappearance of pseudotumor.

Conclusions: The retro-odontoid pseudotumor appears to be related to buckling of the posterior longitudinal ligament. Distraction of the facets probably assists in stretching of the posterior longitudinal ligament. Our experience reconfirms that retro-odontoid pseudotumor could be a manifestation of atlantoaxial instability and need not be directly handled by surgery.